A fractured bone is either connected by an intermedullary nail or by a compression-distraction apparatus in the form of annular members which are mounted around the limb and are connected to the bone fragments by long pins extending through tissue and bone, preferably in crossed alignment, and have their ends firmly connected to the annular members. The latter are interconnected by screws or studs which allow changing their distance from each other in order to shorten or to lengthen the bone.
A typical apparatus is disclosed in SU 971294 which includes two assemblies each containing two rings rigidly connected in spaced relationship by screws and adapted to secure one bone fragment by cross-wise extending pins rigidly connecting the bone to the respective assembly. The two aseemblies are interconnected by spring-loaded screws which effect traction or compression on the fracture in accordance with necessity. The apparatus suffers ffrom the drawback that it provides no means for accurate measuring of the distraction or compression force applied to the fractured bone, and that it provides no means for adjusting the angular alignment of the bone portions with the aim to restore the bone's original shape and curvature.
A second typical apparatus is disclosed in SU 1277959 which includes two outer ring-shaped members surrounding the limb and holding the two fractured bone parts by cross-wise extending pins, and an intermediate ring-shaped member which is not connected to any bone part. The intermediate member is rigidly connected to one of the outer members by screws which permit changing the distance between the two members in accordance with the force to be applied. The intermediate member and the second outer member are not rigidly connected by held in their relative position by three U-shaped springs which have their one end connected to the outer member and are supported on the intermediate member by one steel ball each. Pressure acting on the springs is indicated by annular sensors inside the "U". The main drawback of this apparatus is the impossibility to adjust the angle between the bone fragments, besides the fact that force measurements by means of the annular sensors are very inaccurate. A third drawback is that the components have to be changed for compression and distraction purposes respectively. Still another drawback is the fact that the applied force and change of length have to be continuously read during the entire period of adjustment.
It is the main object of the present invention to avoid these drawbacks and to provide a medical apparatus that will be suitable in promoting rapid and exact healing of a bone fracture in an upper or lower extremity.
It is a second object of the invention to provide an apparatus which will permit application of accurate predesignated tension or pressure force onto the fracture by means of accurate measuring devices.
It is another object to provide means for quick and accurate reading of the forces and length adjustment of the apparatus while it is mounted on the fracture.
It is another object to provide an apparatus which will permit adjustment and possible changing of the angular alignment of the bone fragments so as to restore the original shape of the bone during healing.
Another object is to provide an apparatus which will enable the surgeon to meassure the stiffness of the fracture as well as the angular alignment of the fragments during all stages of healing.